First, abbreviations used in this application document are described as follows:
CIA: collagen-induced arthritis;
HGF: hepatocyte growth factor;
HGFR: hepatocyte growth factor receptor, HGF receptor; and
RA: rheumatoid arthritis.
RA is a disease which causes a nonspecific inflammation mainly in a synovial membrane of a joint, and produces a symptom of polyarthritis in the whole body. There are some prior arts relating to a treating agent for RA (refer to Patent Document 1 and Patent Document 2). However, RA is a complicated disease, and the treatment thereof has been limited to a symptomatic therapy. Thus, a novel therapeutic agent for RA has been desired.    Patent Document 1: JP-A-2002-187856    Patent Document 2: JP-A-2003-183177